These high performance HPLC columns contain high purity spherical silica. Ultra-narrow particle size distribution for excellent column efficiency Sharp, highly symmetrical peaks for acidic, basic and neutral analytes Excellent column to column and batch to batch reproducibility Each column is individually tested and supplied with a test chromatogram. Two generations of Avantor® ACE® Generix® C18 exist: C18 and C18(2) they differ in pore size, carbon load and surface area.